无法使用“ in”运算符在未定义的位置搜索“ d”

问题描述

我正在尝试使用实现Trie的深度优先搜索算法在JavaScript中编写一个难以解决的问题。构建特里树时，我没有收到任何错误；但是，当trie到达dfs算法时，它会提示我“ Type：Error，无法使用'in'运算符在未定义的位置搜索'd'。

我无法弄清楚问题出在我的generate_trie函数中还是我的depth_first_search算法中。您可以在下面找到该程序的所有代码。

// Sample Boggle Dictionary
var boggle_dxctionary = ['apple','pickle','side','sick','mood','cat','cats','man','super','antman','godzilla','dog','dot','sine','cos','signal','bitcoin','cool','kick','zapper'
];

// Sample Boggle Board
var boggle_board = [
  ['c','n','t',],['d','a',['o','o','m',];

var column_length = boggle_board[0].length;
var row_length = boggle_board.length;
var trie_node = {
  'valid': false,'next': {}
};

var neighbors_delta = [
  [-1,-1],[-1,0],1],[0,[1,];

function generate_trie(word,node) {
  if (!(word)) {
    return;
  }
  if ((word[0] in node) == false) {
    node[word[0]] = {
      'valid': (word.length == 1),'next': {}
    };
  }
  generate_trie(word.slice(1,),node[word[0]]);
}

function build_trie(boggle_dxct,trie) {
  for (word = 0; word < boggle_dxct.length; word++) {
    generate_trie(boggle_dxct[word],trie);
  }
  return trie;
}

function get_neighbors(row,column) {
  var neighbors = [];

  for (neighbor = 0; neighbor < neighbors_delta.length; neighbor++) {
    new_row = row + neighbors_delta[neighbor][0];
    new_column = column + neighbors_delta[neighbor][1];

    if (new_row >= row_length || new_column >= column_length || new_row < 0 || new_column < 0) {
      continue;
    }
    neighbors.push([new_row,new_column]);
  }
  return neighbors;
}


function depth_first_search(row,column,visited,trie,current_word,found_words,board) {
  var row_column_pair = [row,column];
  console.log(row_column_pair);

  if (row_column_pair in visited) {
    return;
  }

  letter = board[row][column];
  visited.push(row_column_pair);

  console.log("Up to here is good3");
  console.log(letter);
  if (letter in trie) {
    current_word = current_word + letter;
    console.log("Up to here is good4");
    if (trie[letter]['valid']) {
      found_words.push(current_word);
    }

    neighbors = get_neighbors(row,column);
    for (n = 0; n < neighbors.length; n++) {
      console.log("Up to here is good5");
      depth_first_search(neighbors[n][0],neighbors[n][1],visited.slice(0,visited.length),trie[letter],board);
      console.log("Up to here is good6");
    }
  }
}

function main(trie_node,board) {
  trie_node = build_trie(boggle_dxctionary,trie_node);
  found_words = [];

  for (r = 0; r < row_length; r++) {
    console.log("Up to here is good1");
    for (c = 0; c < column_length; c++) {
      var visited = [];
      var current_word = '';
      depth_first_search(r,c,trie_node,board);
      console.log("Up to here is good2");
    }
  }
  console.log(found_words);
}
main(trie_node,boggle_board);

解决方法

问题是您没有在letter中将depth_first_search声明为局部变量。因此，当它在for循环中调用自身时，递归调用将更改letter的值，而trie[letter]则找不到任何内容。

除非有特殊原因，否则

始终都使用局部变量。我在下面的代码中添加了var声明。

// Sample Boggle Dictionary
var boggle_dxctionary = ['apple','pickle','side','sick','mood','cat','cats','man','super','antman','godzilla','dog','dot','sine','cos','signal','bitcoin','cool','kick','zapper'
];

// Sample Boggle Board
var boggle_board = [
  ['c','n','t',],['d','a',['o','o','m',];

var column_length = boggle_board[0].length;
var row_length = boggle_board.length;
var trie_node = {
  'valid': false,'next': {}
};

var neighbors_delta = [
  [-1,-1],[-1,0],1],[0,[1,];

function generate_trie(word,node) {
  if (!(word)) {
    return;
  }
  if ((word[0] in node) == false) {
    node[word[0]] = {
      'valid': (word.length == 1),'next': {}
    };
  }
  generate_trie(word.slice(1,),node[word[0]]);
}

function build_trie(boggle_dxct,trie) {
  for (var word = 0; word < boggle_dxct.length; word++) {
    generate_trie(boggle_dxct[word],trie);
  }
  return trie;
}

function get_neighbors(row,column) {
  var neighbors = [];

  for (var neighbor = 0; neighbor < neighbors_delta.length; neighbor++) {
    var new_row = row + neighbors_delta[neighbor][0];
    var new_column = column + neighbors_delta[neighbor][1];

    if (new_row >= row_length || new_column >= column_length || new_row < 0 || new_column < 0) {
      continue;
    }
    neighbors.push([new_row,new_column]);
  }
  return neighbors;
}


function depth_first_search(row,column,visited,trie,current_word,found_words,board) {
  var row_column_pair = [row,column];
  console.log(row_column_pair);

  if (row_column_pair in visited) {
    return;
  }

  var letter = board[row][column];
  visited.push(row_column_pair);

  console.log("Up to here is good3");
  console.log(letter);
  if (letter in trie) {
    current_word = current_word + letter;
    console.log("Up to here is good4");
    if (trie[letter]['valid']) {
      found_words.push(current_word);
    }

    var neighbors = get_neighbors(row,column);
    for (n = 0; n < neighbors.length; n++) {
      console.log("Up to here is good5");
      depth_first_search(neighbors[n][0],neighbors[n][1],visited.slice(0,visited.length),trie[letter],board);
      console.log("Up to here is good6");
    }
  }
}

function main(trie_node,board) {
  trie_node = build_trie(boggle_dxctionary,trie_node);
  var found_words = [];

  for (r = 0; r < row_length; r++) {
    console.log("Up to here is good1");
    for (c = 0; c < column_length; c++) {
      var visited = [];
      var current_word = '';
      depth_first_search(r,c,trie_node,board);
      console.log("Up to here is good2");
    }
  }
  console.log(found_words);
}

main(trie_node,boggle_board);